Charlie67j

Greetings all,

I'm new here and have been searching everywhere for some information that could help me figure out whats going on with my 2008 C300 Sport. I'm getting the Hood Open indication on the instrument cluster with the constant dinging that I can't clear or make go away. I've been troubleshooting this issue and can't find a solution. I would humbly ask for some other ideas from the community. I'll explain a little more of what I've done to this point.

1. Started getting this error message, which immediately made me start searching the interwebs for possible scenarios that could cause this issue. The obvious one is that the hood sensor was bad, broken, fell off, etc.
2. When I couldn't find anything obvious, I turned to my local independent shop and had them take a look. They don't have a Star diagnostics capability, so the information was limited. They tried searching for the issue and came up empty. They said that I should try the MB Dealer and run it through the diagnostics.
3. Took it to the dealer. They came back stating that the instrument cluster needed to be changed, $2,500 in parts + labor. They said that they could "see the signal from the switch, but the IC won't stop showing the warning so it must be the IC". This didn't feel right to me, so I thanked them for their time and took the car back home.
4. In between the time that the car was at my local shop and at the dealer, I ordered a MB SD Connect C5 Star Diagnosis Xentry, ect., and Laptop setup because I like to troubleshoot and understand my own stuff. Admittedly, I'm a total noob at using the applications at this point, but I do something similar for a living and am comfortable when it comes to software and electronics.
5. I got the car home and got it connected to my new Star Diagnosis system with no problems. After playing around and checking the active faults, I found that the fault was coming from the front SAM and was indeed throwing a fault. In my mind, this most likely eliminates the instrument cluster as being faulty since there is actually a fault in the SAM. The instrument cluster is doing its job and reporting the fault.
6. While going through the steps of troubleshooting I tried several things.
   1. Removing the hood switch and checking it with my Fluke DMM. I was expecting this to be a standard NO or NC contact, but was actually getting some strange readings. In the engaged, hood locked state, I was seeing something like 2Meg, in the open position I was seeing something closer to 100K.
   2. I tried to jumper the connection through the switch, no change.
   3. I tried to replicate the readings that I saw with my DMM using resistors and a capacitor. I did notice that when my DMM was connected the leakage seems to change the reading so I figured that there might be a cap inline in the switch. No Change.
   4. I tried keeping the plug unhooked with an open circuit, no change. Other than the fault would go away, but of course the car thinks the hood is open. No change.
   5. I ordered and installed a new switch, checking it first with the DMM to see if the values were any different. They were. No change.
   6. Many versions of the above, checking grounding points, cleaning them, putting dielectric grease on them, checking continuity, voltages, etc. No change.
7. This is when I noticed something that I had missed. All of this time I've been looking at and working on the driver's side hood switch. The Fault code (B181E2A) in XENTRY is actually not for the 'S62/43' hood contact switch, but for the 'S62/42 (Right engine hood contact switch)'. Okay, now we're getting somewhere. The problem is that in all the documentation that I have checked ( I also signed up for a week on Startekinfo.com) my car doesn't have the right side switch. I can't find it either. All of the pictures for locations indicate the 'S62/43" on the driver's side.
8. So, now I'm looking over the information that I can find to understand why my car "thinks" I have two hood switches. Or does it have two switches and I'm simply unable to find it? Am I reading the documentation wrong or something? Also looking at the functional schematic downloaded from Startek, I'm having a hard time deciphering their drawing standards. The switch that I've been messing with on the driver's side has the Brown/Red wire so that is inline with the schematic reference for the 'S62/43' since 'S62/42' should have a Brown/Blue wire. The schematic shows that it goes into a plug on pin 9, but the plug is labeled as "20M". I can find no reference to what 20M is, or where to find it. 20M is connected by blue wire to another rectangle with what appears to be a diode in the center. There is no symbol reference in the documentation that I can find that shows this symbol. Anyone know? I'm attaching the schematic as a PDF.

I'm hoping that someone here can give me a sanity check and say that I"m not missing something obvious. I'll attach the XENTRY output files and the prints that I'm working from. All of the details about the car can be found in the PDFs. Thank you in advance to anyone that has an idea about how I might proceed in a positive direction in my struggles here.

Cheers!

Charlie67j

The print didn't make it through. I'm attaching it here.

Charlie67j

Okay, as I continue to troubleshoot this my suspicions are the the Indie shop that does some of my work tried to update my Front Driver's Side SAM module. Since they don't have the ability to perform an online SCN coding of the module they completed an offline update utilizing one of many methods. My belief is that the firmware version for the module that they used was for a W204, but not the exact version for my car. I believe that other W204 models have two hood switches 'S62/43' & 'S62/42' but my C300 Sport is only coded to use the 'S62/43' switch from the factory. The next step is to perform an online SCN to reinitialize the module to factory settings and see if this fixes the issue. I'll report back if this was the case, if nothing else but to close this thread.

Cheers!

Charlie67j

Here's the final update. I was able to get the Gateway, Front SAM and Rear SAM modules SCN coded this morning online. My suspicions were confirmed that the issue was created by the Indie shop that tried to fix an issue with an offline module upgrade. I guess this is a good lesson that offline coding can be done, but you really need to know about variant coding to configure the module with the proper systems as installed on each particular car. The thing that still troubles me is that the dealer wanted to replace my instrument cluster and didn't properly diagnose even the symptoms of the error. Without my computer and MUX, I would have never known any better. If you plan to troubleshoot or work on your own car, you need a laptop, software and MUX or you stand no chance. You can find them for the cost of a service and minor repairs at the dealer. Everything, EVERYTHING, in these cars is connected to the modules and gets/receives a signal that can be monitored. Some might see this as a negative, but you really couldn't ask for more if you are trying to troubleshoot a problem.

I hope that my experience will be helpful to others at some point.

Cheers!

Maher Aboudaye

Hey, thanks for the info. I'm having this same issue. How can I update the coding?

Charlie67j

If you don't have the hardware, a dealer or a independent shop owner that has the ability to code the car will be necessary. Personally, I purchased a version of the software and the communications hardware to interface with the car. This was a gamble, but was much less money that what the dealer wanted to do, which in the end was the wrong diagnosis anyway. If you decide to get your own hardware, do plenty of research on which one to buy as there are different levels of fake units. Some fakes are good and will work fine, others not so. I then had someone remotely code my car for a small fee. You would need to do some Google searching to find the source for that gray market information. I'll not post that here, it's been long enough that I probably don't have updated information. In the end, I think finding a small local shop that can do it is the least expensive and simplest option.

Good luck.

Moto_Guzzi

This was a good one.

Maher Aboudaye

A local Mercedes shop wants me to replace the front sam saying it's the source of the problem. I do have the airbag light on... Could it possibly be related? Also have an autel with pass through coding capabilities.

Really stumped with this. If anyone knows how to code it out, I would really appreciate it.

bcruz

Can you provide your contact for programming SAM. I have same issue with my hood.